docs: def fetch_command(self, global_options, subcommand):
          """
          Tries to fetch the given subcommand, printing a message with the
          appropriate command called from the command line (usually
          "uliweb") if it can't be found.
          """
          commands = self.get_commands(global_options)
          try:
              klass = commands[subcommand]
          except KeyError:
              sys.stderr.write("Unknown command: %r\nType '%s help' for usage.\nMany commands will only run at project directory, maybe the directory is not right.\n" % \
                  (subcommand, self.prog_name))
              sys.exit(1)
          return klass